Eliminate some code duplication parsing an exponent as an integer

serde_json/src/de.rs

@@ -222,17 +222,20 @@ impl<Iter> Deserializer<Iter>
         Ok(accum)
     }
 
-    fn parse_decimal(&mut self, res: f64) -> Result<f64> {
+    fn parse_decimal(&mut self, mut res: f64) -> Result<f64> {
         try!(self.bump());
 
+        let mut dec = 0.1;
+
         // Make sure a digit follows the decimal place.
         match self.ch_or_null() {
-            b'0' ... b'9' => (),
+            c @ b'0' ... b'9' => {
+                try!(self.bump());
+                res += (((c as u64) - (b'0' as u64)) as f64) * dec;
+            }
              _ => { return Err(self.error(ErrorCode::InvalidNumber)); }
         }
 
-        let mut res = res;
-        let mut dec = 1.0;
         while !self.eof() {
             match self.ch_or_null() {
                 c @ b'0' ... b'9' => {
@@ -250,30 +253,30 @@ impl<Iter> Deserializer<Iter>
     fn parse_exponent(&mut self, mut res: f64) -> Result<f64> {
         try!(self.bump());
 
-        let mut exp: u64 = 0;
-        let mut neg_exp = false;
-
-        if self.ch_is(b'+') {
-            try!(self.bump());
-        } else if self.ch_is(b'-') {
-            try!(self.bump());
-            neg_exp = true;
-        }
+        let pos = match self.ch_or_null() {
+            b'+' => { try!(self.bump()); true }
+            b'-' => { try!(self.bump()); false }
+            _ => { true }
+        };
 
         // Make sure a digit follows the exponent place.
-        match self.ch_or_null() {
-            b'0' ... b'9' => (),
+        let mut exp = match self.ch_or_null() {
+            c @ b'0' ... b'9' => {
+                try!(self.bump());
+                (c as u64) - (b'0' as u64)
+            }
             _ => { return Err(self.error(ErrorCode::InvalidNumber)); }
-        }
-        while !self.eof() {
+        };
+
+        loop {
             match self.ch_or_null() {
                 c @ b'0' ... b'9' => {
+                    try!(self.bump());
+
                     exp = try_or_invalid!(self, exp.checked_mul(10));
                     exp = try_or_invalid!(self, exp.checked_add((c as u64) - (b'0' as u64)));
-
-                    try!(self.bump());
                 }
-                _ => break
+                _ => { break; }
             }
         }
 
@@ -283,10 +286,10 @@ impl<Iter> Deserializer<Iter>
             return Err(self.error(ErrorCode::InvalidNumber));
         };
 
-        if neg_exp {
-            res /= exp;
-        } else {
+        if pos {
             res *= exp;
+        } else {
+            res /= exp;
         }
 
         Ok(res)

serde_tests/tests/test_json.rs

@@ -708,7 +708,7 @@ fn test_parse_number_errors() {
         ("1e+", Error::SyntaxError(ErrorCode::InvalidNumber, 1, 3)),
         ("1a", Error::SyntaxError(ErrorCode::TrailingCharacters, 1, 2)),
         ("777777777777777777777777777", Error::SyntaxError(ErrorCode::InvalidNumber, 1, 20)),
-        ("1e777777777777777777777777777", Error::SyntaxError(ErrorCode::InvalidNumber, 1, 22)),
+        ("1e777777777777777777777777777", Error::SyntaxError(ErrorCode::InvalidNumber, 1, 23)),
     ]);
 }
 
@@ -735,13 +735,21 @@ fn test_parse_f64() {
     test_parse_ok(vec![
         ("0.0", 0.0f64),
         ("3.0", 3.0f64),
+        ("3.00", 3.0f64),
         ("3.1", 3.1),
         ("-1.2", -1.2),
         ("0.4", 0.4),
         ("0.4e5", 0.4e5),
+        ("0.4e+5", 0.4e5),
         ("0.4e15", 0.4e15),
-        ("0.4e-01", 0.4e-01),
-        (" 0.4e-01 ", 0.4e-01),
+        ("0.4e+15", 0.4e15),
+        ("0.4e-01", 0.4e-1),
+        (" 0.4e-01 ", 0.4e-1),
+        ("0.4e-001", 0.4e-1),
+        ("0.4e-0", 0.4e0),
+        ("0.00e00", 0.0),
+        ("0.00e+00", 0.0),
+        ("0.00e-00", 0.0),
     ]);
 }